1. Field of the Invention
The present invention relates to a force-applying input device for applying a force which is electrically controlled by a manually operated operation section. More particularly, the present invention relates to means for applying a force which is similar to frictional force of a mechanism to an operation section of a joystick input device.
2. Description of the Related Art
In recent years, a force-applying biwire input device (hereinafter referred to as a “force-applying input device” in the specification) has been proposed in place of a mechanical input device for transmitting an operation state of an operation section to a control section through a mechanism. The force-applying input device applies a predetermined force to an operation section by converting an operation state of the operation section into an electrical signal, by transmitting the electrical signal to a control section, and by controlling drive of an actuator, such as an electric motor, and increasees its range of application. Various types of force-applying input devices are available. They include a sliding force-applying input device, a lever force-applying input device, a rotary force-applying input device, and a joystick force-applying input device. The sliding and the lever force-applying input devices allow reciprocatory operation of the operation section in only one direction. The rotary force-applying input device allows reciprocatory rotational operation of the operation section only around one axis. The joystick force-applying input device allows operation of the operation section in any direction.
In the force-applying input device, various forces can be applied to the operation section by controlling the driving of the actuator, thereby making it possible for an operator to feel a force in accordance with the operation state of the operation section. However, a force-applying input device which can apply with good repeatability a force which is similar to frictional force of a mechanism felt by the operator when the operator operates the operation section of a mechanical input device has not yet been proposed.
Applying a force which is similar to frictional force of a mechanism to the operation section in the force-applying input device is particularly important in reducing differences in operational feel experienced by the operator when changing from a mechanical input device to the force-applying input device in order to prevent, for example, improper operation of or a delay in operation of the operation section due to inexperience of the operator. Therefore, high expectations are placed on the production of such a force-applying input device.
The present inventors have not been able to find any related-art documents disclosing a description related to the present invention up to the present time.
In order to apply a force which is similar to frictional force of a mechanism felt by an operator who operates an operation section of a mechanical input device to the operation section of the force-applying input device, the sliding force-applying input device, the lever force-applying input device, and the rotary force-applying input device must satisfy the following three Conditions (1) to (3):
(1) when the operation section is operated in one direction from a start position, driving force of the actuator, that is, an external force with respect to the operation section, must act in a direction opposite to the operation direction of the operation section,
(2) from a time in which the operation is started to a time in which the operation is stopped, the magnitude of the external force acting upon the operation section must be substantially constant, and
(3) after stopping the operation, the operation section must be stably held.
The joystick force-applying input device must satisfy the aforementioned three Conditions (1) to (3), and Condition (4) in which the aforementioned three Conditions (1) to (3) must be satisfied when the operation direction of the operation section is changed during the operation of the operation section.
Conditions (1) and (2) are relatively easily satisfied by the sliding force-applying input device, the lever force-applying input device, the rotary force-applying input device, and the joystick force-applying input device by detecting the direction and amount of operation of the operation section by a position sensor, and by controlling the driving of the actuator by a control section based on a position signal output from the position sensor so that a predetermined force corresponding to frictional force is applied in the direction opposite to the operation direction of the operation section.
However, when such structures are used, application of a predetermined external force which is similar to the frictional force to the operation section is continued even after the operator stops operating the operation section. Therefore, each time the operator takes his/her hand off the operation section, the following is repeated: the operation section returns in the direction opposite to the operation direction prior to stopping the operation by the external force, the position sensor detects the direction and amount of this returning movement, and the actuator applies the predetermined external force, which is similar to the frictional force, in a direction opposite to the returning direction. Consequently, Condition (3) cannot be satisfied.
In addition to the aforementioned disadvantages, the joystick force-applying input device has the disadvantage that, when the operation direction of the operation section is changed during the operation of the operation section, a constant external force can no longer be applied in the direction opposite to the operation direction of the operation section. Therefore, the joystick force-applying input device cannot satisfy Conditions (1) to (3).
That is, in the case in which the direction and amount of operation of the operation section is detected by the position sensor, the control section controls the driving of the actuator based on the position signal output from the position sensor so that the predetermined external force corresponding to the frictional force is applied in a direction opposite to the direction of the operation section. When the operation section is operated in an X axis direction, and then is operated in a Y axis direction from a position reached by the operation in the X axis direction, Conditions (1) and (2) cannot be satisfied. This is because, a resultant external force component corresponding to the amount of operation in the X axis direction and to the amount of operation in the Y axis direction is applied to the operation section with a magnitude of (√2)·Fmax (when the magnitudes of the external force components in the respective directions are Fmax), and at an angle of 45 degrees with respect to the X and Y axis directions based on the position signal output from the position sensor. In addition, when the operator takes his/her hand off the operation section, the operation section returns at an angle of 45 degrees with respect to the X and Y axis directions due to: the resultant force that acts upon the operation section, detection of the direction and amount of this returning movement by the position sensor, and application of a predetermined external force which is similar to the frictional force by the actuator in a direction opposite to the returning direction. These actions are repeated. Therefore, Condition (3) cannot be satisfied.